Wafer level packaging of light emitting diodes (leds)

ABSTRACT

An LED wafer includes LED dies on an LED substrate. The LED wafer and a carrier wafer are joined. The LED wafer that is joined to the carrier wafer is shaped. Wavelength conversion material is applied to the LED wafer that is shaped. Singulation is performed to provide LED dies that are joined to a carrier die. The singulated devices may be mounted in an LED fixture to provide high light output per unit area.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of provisional Patent ApplicationNo. 61/621,746, filed Apr. 9, 2012, entitled Wafer Level Packaging ofLight Emitting Diodes (LEDs), assigned to the assignee of the presentinvention, the disclosure of which is hereby incorporated herein byreference in their entirety as if set forth fully herein.

BACKGROUND

This invention relates to light emitting devices and assemblies andmethods of manufacturing the same, and more particularly, to LightEmitting Diodes (LEDs) and assemblies thereof.

LEDs are widely known solid-state lighting elements that are capable ofgenerating light upon application of voltage thereto. LEDs generallyinclude a diode region having first and second opposing faces, andinclude therein an n-type layer, a p-type layer and a p-n junction. Ananode contact ohmically contacts the p-type layer and a cathode contactohmically contacts the n-type layer. The diode region may be epitaxiallyformed on a substrate, such as a sapphire, silicon, silicon carbide,gallium arsenide, gallium nitride, etc., growth substrate, but thecompleted device may not include a substrate. The diode region may befabricated, for example, from silicon carbide, gallium nitride, galliumphosphide, aluminum nitride and/or gallium arsenide-based materialsand/or from organic semiconductor-based materials. Finally, the lightradiated by the LED may be in the visible or ultraviolet (UV) regions,and the LED may incorporate wavelength conversion material such asphosphor.

LEDs are increasingly being used in lighting/illumination applications,with a goal being to provide a replacement for the ubiquitousincandescent light bulb.

SUMMARY

Various embodiments described herein provide methods of fabricating aplurality of Light Emitting Diodes (LEDs). An LED wafer is provided thatincludes a plurality of LED dies on an LED substrate, the plurality ofLED dies including anode and cathode contacts on a face thereof that isremote from the LED substrate. A carrier wafer is also provided. The LEDwafer and the carrier wafer are joined, so that the anode and cathodecontacts are adjacent the carrier wafer and the LED substrate is remotefrom the carrier wafer. The LED wafer that is joined to the carrierwafer is shaped. Wavelength conversion material is applied to the LEDwafer that is shaped. Finally, singulation is performed on the carrierwafer and the LED wafer, to provide a plurality of LED dies, arespective one of which is joined to a respective carrier die, andhaving a length and width similar to the carrier die to which it isjoined.

In some embodiments, the carrier wafer is scribed to define theplurality of carrier dies that are of similar length and width as theplurality of LED dies. The scribing may be performed before or after thejoining. In other embodiments, the shaping comprises beveling the LEDsubstrate. In still other embodiments, the shaping comprises texturingthe LED substrate. In yet other embodiments, the shaping comprisesthinning or removing the LED substrate, and the thinning or removing maybe followed by texturing the LED dies. In yet other embodiments, theshaping comprises beveling the LED dies.

In some embodiments, singulating is followed by removing the respectivecarrier die. In other embodiments, singulating is followed by mountingat least one of the LED dies directly on a light fixture mounting boardand mounting the light fixture mounting board including the at least oneof the LED dies mounted directly thereon, in a light fixture housing toprovide a light fixture. In still other embodiments, the mounting atleast one of the LED dies directly on a light fixture mounting board andthe mounting the light fixture mounting board in a light fixture housingare performed without providing a dome on the at least one of the LEDdies.

In still other embodiments, the carrier wafer includes arrays ofcontacts on opposing faces thereof and an array of through-vias thatelectrically connect respective contacts on the opposing faces to oneanother. In other embodiments, the arrays of contacts on the opposingfaces have different dimensions therebetween.

LEDs according to various other embodiments described herein may includea semiconductor LED die that includes an LED epi region and a carrierdie that is electrically connected to the LED die, wherein the LED epiregion and the carrier die have sides that are within 100 μm of oneanother in length. In some embodiments, the LED epi region and thecarrier die have same side lengths. In other embodiments, the LEDproduces at least 100, and in some embodiments at least 150, and in yetother embodiments at least about 200 lumens, of cool white light in someembodiments, per watt per square millimeter. In other embodiments, theLED produces at least 30 and in some embodiments at least 70, and in yetother embodiments at least about 140 lumens of warm white light per wattper square millimeter. In some embodiments, an anode and a cathode areboth provided on the carrier die, remote from the LED die, and in otherembodiments, the LED die further includes a substrate.

Light emitting diodes according to other embodiments can comprise asemiconductor LED die that includes an LED epi region and a carrier diethat is electrically connected to the LED die, wherein the LED epiregion and the carrier dies have sides that are within about 15% of oneanother in length. In other embodiments, the LED epi region and carrierdie have areas that are within 70% of one another, within 85% of oneanother, or have same areas. In some embodiments, the LED epi region andthe carrier die have the same side lengths. In still other embodiments,the LED may produce at least 45, and in some embodiments at least 100,and in other embodiments at least about 200 lumens, of cool white lightin some embodiments, per watt per square millimeter. In still otherembodiments, the LED may produce at least 30, and in some embodiments atleast 70, and in other embodiments at least about 140 lumens of warmwhite light. In some embodiments, an anode and a cathode are bothprovided on the carrier die, remote from the LED die, and in otherembodiments, the LED die further includes a substrate.

In still other embodiments, an LED comprises a semiconductor LED die anda carrier die that is electrically connected to the LED die, wherein theLED produces at least 45 lumens, of cool white light in someembodiments, per watt per square millimeter of area of the carrier die.In some embodiments, the LED produces at least 100 lumens, and in otherembodiments at least about 200 lumens, of cool white light in someembodiments, per watt per square millimeter of the area of the carrierdie. In still other embodiments, the LED produces at least 30 lumens,and in other embodiments at least 70 lumens, and in still otherembodiments at least about 140 lumens of warm white light per squaremillimeter of area of the carrier die. In still other embodiments, theLED produces at least 45 lumens, and in some embodiments at least 100lumens, and in other embodiments at least about 200 lumens, of coolwhite light in some embodiments, per watt per cubic millimeter of volumeof the LED. In yet other embodiments, the LED produces at least 30lumens, and in some embodiments at least 70 lumens, and in otherembodiments at least about 140 lumens of warm white light per cubicmillimeter of volume of the LED. In some embodiments, an anode and acathode are both provided on the carrier die, remote from the LED die,and in other embodiments, the LED die further includes a substrate.

LEDs according to other embodiments include a semiconductor LED die anda carrier die that is electrically connected to the LED die, wherein thecarrier die has an area of less than about 2 square millimeters, and insome embodiments less than about 1 square millimeter, and in otherembodiments, an area of about 0.5 square millimeter or less. In any ofthese embodiments, the LED may have a height of about one millimeter. Instill other embodiments, an LED comprises a semiconductor LED die and acarrier die that is electrically connected to the LED die, wherein theLED has a height of less than about 1.5 millimeters, and in someembodiments less than about 1 millimeter.

LEDs according to still other embodiments may include a semiconductorLED die comprising a semiconductor LED die that includes inner and outerfaces and a plurality of sidewalls therebetween, and a carrier die thatincludes inner and outer faces and a plurality of sidewallstherebetween, wherein the inner face of the LED die is electricallyconnected to the inner face of the carrier die. A phosphor layer extendsdirectly on the outer face of the LED die, directly on the plurality ofsidewalls of the LED die and directly on the plurality of sidewalls ofthe carrier die. In some embodiments, the phosphor layer covers theouter face of the LED die and the plurality of sidewalls of the LED dieand partially covers the plurality of sidewalls of the carrier die. Inyet other embodiments, the phosphor layer protrudes beyond the carrierdie in a direction along the faces of the carrier die.

Yet other embodiments may include a protective layer on the phosphorlayer, remote from the LED die and the carrier die. In some embodiments,the phosphor layer comprises phosphor particles in a silicone binder,and the protective layer comprises a silicon layer that is free of thephosphor particles therein.

In still other embodiments, the outer face of the carrier die isconfigured for surface mounting of the LED. Moreover in someembodiments, the outer face of the carrier die includes a feature, suchas a notch in a contact, configured to allow identification of anorientation of the LED.

LEDs according to still other embodiments may include a carrier, an LEDepi region, a primary optic distinct from the LED epi region and aphosphor layer, wherein the carrier, LED epi region, primary optic andphosphor layer have outer edges that are within 100 μm of one another,and in other embodiments have same size outer edges. As used herein, a“primary optic” means an optical element that causes the luminous fluxfrom the LED to assume a specific illumination pattern. In someembodiments described herein, a substrate of the LED epi region mayassume the role of a primary optic.

LEDs according to any of the embodiments described herein may becombined with a light fixture mounting board on which the carrier die isdirectly mounted and a light fixture housing in which the light fixturemounting board is mounted, to provide a light fixture. The light fixtureis free of a dome between the carrier die and the light fixture housing.

An LED light fixture according to various embodiments described hereinmay include a light fixture mounting board, a plurality of LEDs directlymounted on the light fixture mounting board and a light fixture housingin which the light fixture mounting board including the plurality ofLEDs thereon is mounted. The light fixture is free of a dome between arespective LED and the light fixture housing. The plurality of LEDs maycomprise a plurality of semiconductor LED dies that are directly mountedon the light fixture mounting board without a carrier die therebetween.

Finally, methods of manufacturing LED light fixtures according to otherembodiments described herein may include fabricating a plurality of LEDwafers including wavelength converting material thereon at chip factory,dicing the LED wafers including the wavelength converting materialthereon to produce a plurality of LED dies, and mounting the LED dies ona light fixture mounting board at a module factory or at a fixturefactory and mounting the light fixture mounting board in a light fixtureat a fixture factory. The fabricating, the dicing and the mountingbypass LED packaging factories. In these embodiments, the chip, moduleand fixture factories do not perform an operation of providing domes onthe plurality of LED dies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1P and 1S-1U are cross-sections of one or more LEDs duringintermediate and final wafer level packaging, according to variousembodiments described herein.

FIGS. 1Q and 1R are bottom views of a carrier substrate of FIG. 1K.

FIG. 2 is a cross-section of an LED die in a light fixture according tovarious embodiments described herein.

FIG. 3 is a flowchart of LED fixture manufacturing according to variousembodiments described herein.

FIG. 4 is a flowchart of conventional fixture manufacturing.

FIG. 5 is a more detailed flowchart of conventional fixturemanufacturing.

FIG. 6 is a cross-section of LED dies in a light fixture housingaccording to various embodiments described herein.

FIGS. 7 and 8 are flowcharts of wafer level packaging of LEDs accordingto various other embodiments described herein.

FIG. 9A is a cross-section of a mounting board and a plurality of LEDdies mounted thereon according to various embodiments described herein.

FIG. 9B is a plan view of FIG. 9A.

FIG. 10A is a cross-section of a conventional packing of LED dies on acarrier substrate.

FIG. 10B is a plan view of FIG. 10A,

FIG. 11 illustrates performance of wafer level packaged LEDs accordingto various embodiments described herein.

FIG. 12A is a photograph of a prototype LED according to variousembodiments described herein, taken from the side.

FIG. 12B is a photograph of a prototype LED according to variousembodiments described herein, taken from the bottom.

FIG. 12C is another photograph of a prototype LED according to variousembodiments described herein, taken from the side.

FIG. 12D is a photograph of a prototype LED according to variousembodiments described herein, taken from the top.

FIG. 12E is another photograph of a prototype LED according to variousembodiments described herein, taken from the top.

FIG. 13A is a photograph of a prototype LED according to variousembodiments described herein, taken from the bottom.

FIG. 13B is a photograph of a prototype LED according to variousembodiments described herein, taken from the top.

FIG. 13C is a side view of a prototype LED according to variousembodiments described herein.

FIG. 14 is a series of photographs of prototype LEDs according tovarious embodiments described herein, after wafer singulation andbiasing of a backside contact.

FIG. 15 is a photograph illustrating relative sizes of a prototype LEDaccording to various embodiments described herein (far right side) andother LEDs.

FIG. 16 is a series of photographs of prototype LEDs according tovarious embodiments described herein after singulation, mounted on amounting board and mounted in an LED fixture.

DETAILED DESCRIPTION

The present invention now will be described more fully with reference tothe accompanying drawings, in which various embodiments are shown. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the size and relative sizes oflayers and regions may be exaggerated for clarity. Like numbers refer tolike elements throughout.

It will be understood that when an element such as a layer, region orsubstrate is referred to as being “on” another element, it can bedirectly on the other element or intervening elements may also bepresent. Furthermore, relative terms such as “beneath” or “overlies” maybe used herein to describe a relationship of one layer or region toanother layer or region relative to a substrate or base layer asillustrated in the figures. It will be understood that these terms areintended to encompass different orientations of the device in additionto the orientation depicted in the figures. Finally, the term “directly”means that there are no intervening elements. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items and may be abbreviated as “/”.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Embodiments of the invention are described herein with reference tocross-sectional and/or other illustrations that are schematicillustrations of idealized embodiments of the invention. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments of the invention should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described as arectangle will, typically, have rounded or curved features due to normalmanufacturing tolerances. Thus, the regions illustrated in the figuresare schematic in nature and their shapes are not intended to illustratethe precise shape of a region of a device and are not intended to limitthe scope of the invention, unless otherwise defined herein.

Unless otherwise defined herein, all terms (including technical andscientific terms) used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand this specification and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Some embodiments now will be described generally with reference togallium nitride (GaN)-based light emitting diodes on silicon carbide(SiC)-based growth substrates for ease of understanding the descriptionherein. However, it will be understood by those having skill in the artthat other embodiments of the present invention may be based on avariety of different combinations of growth substrate and epitaxiallayers. For example, combinations can include AlGaInP diodes on GaPgrowth substrates; InGaAs diodes on GaAs growth substrates; AlGaAsdiodes on GaAs growth substrates; SiC diodes on SiC or sapphire (Al₂O₃)growth substrates and/or a Group III-nitride-based diode on galliumnitride, silicon carbide, aluminum nitride, sapphire, zinc oxide and/orother growth substrates. Moreover, in other embodiments, a growthsubstrate may not be present in the finished product. For example, thegrowth substrate may be removed after forming the light emitting diode,and/or a bonded substrate may be provided on the light emitting diodeafter removing the growth substrate. In some embodiments, the lightemitting diodes may be gallium nitride-based LED devices manufacturedand sold by Cree, Inc. of Durham, N.C.

Various embodiments described herein can increase the lumen/dollarperformance of LEDs by performing packaging-like process steps at thewafer level, to allow reduction of handling and assembling of discretelevel LED dies or chips into a package. Thus, various embodimentsdescribed herein can merge chip or die fabrication and packaging intofewer steps, to thereby allow leveraging of the parallel process costreduction available by performing wafer level processing of the dierather than component level processing. Various embodiments describedherein can move die and component singulation to the end of the LED lampmanufacturing line. Moreover, various embodiments described herein canalso reduce redundant characterization steps between the LED die and LEDpackage testing, which can allow further reduction in manufacturingcosts, such as labor, work-in-process time and capital expense. Finally,various embodiments described herein can tightly pack LED dies on amounting board to allow increased luminous efficiency.

Various embodiments described herein may arise from recognition that,conventionally, LED dies are singulated and sorted, and placed upon diesheets, which are shipped to a components factory, only to have the diesremoved from the die sheets and repopulated onto panels. Accordingly,conventional LED manufacturing begins with a wafer, singulates the waferand then basically reassembles the wafer, only to repeat the process ofsingulation followed by testing and measurements again. Variousembodiments described herein can provide methods of fabricating LEDs andmethods of manufacturing LED light fixtures that can at least partiallyreduce or eliminate these redundancies. Moreover, various embodimentsdescribed herein can provide LEDs and LED light fixtures somanufactured.

FIG. 1A is a cross-sectional view of an LED wafer including a pluralityof LED dies. Referring to FIG. 1A, the LED wafer 100 includes dioderegions 110 having first and second opposing faces 110 a, 110 b,respectively, and including therein an n-type layer 112 and a p-typelayer 114. Other layers or regions may be provided, which may includequantum wells, buffer layers, etc., that need not be described herein.Moreover, the n-type layer 112 and the p-type layer 114 may be adjacentone another to form a p-n junction or may be spaced apart from oneanother. Either or both layers may be at a surface of the diode region110 or may be buried within the diode region. Anode contacts 160ohmically contact the p-type layer 114 and extends on the first face 110a. The anode contacts 160 may directly ohmically contact the p-typelayer 114, or may ohmically contact the p-type layer 114 by way of oneor more conductive vias 162 and/or other intermediate layers. Cathodecontacts 170 ohmically contact the n-type layer 112 and also extend onthe first face 110 a. The cathode contacts may directly ohmicallycontact the n-type layer 112, or may ohmically contact the n-type layer112 by way of one or more conductive vias 172 and/or other intermediatelayers. As illustrated in FIG. 1A, the anode contacts 160 and thecathode contacts 170 that both extend on the first face 110 a arecoplanar.

The diode region 110 also may be referred to herein as an “LED epiregion” or simply as an “LED epi”, because it is typically formedepitaxially on a substrate 120. For example, a Group III-nitride basedLED epi 110 may be formed on a silicon carbide growth substrate. In someembodiments, the growth substrate may be present in the finishedproduct. In other embodiments, the growth substrate may be thinned orremoved. In still other embodiments, another substrate may be providedthat is different from the growth substrate, and the other substrate maybe bonded to the LED after removing the growth substrate. The LED epi110 defines a plurality of LED dies 110′.

As also shown in FIG. 1A, a substrate 120, such as a transparent siliconcarbide growth substrate or a transparent sapphire growth substrate, isincluded on the second face 110 b of the diode region 110. The substrate120 includes an inner face 120 c adjacent the second face 110 b of thediode region 110 and an outer face 120 b, remote from the inner face 120c.

FIG. 1B illustrates a carrier wafer 180 that includes a body 182 thatmay comprise aluminum nitride (AlN), silicon and/or aluminum oxide. Inother embodiments, metal core substrates, printed circuit boards and/orother carrier wafers may be used. The carrier wafer 180 includes acarrier wafer face 182 a, and an anode pad 184 and a cathode pad 186thereon. The anode and cathode pads may comprise silver-plated copperand/or other conductive materials. A packaged device anode 192 and apackaged device cathode 194 may be provided on a second face 182 b ofthe body 182, and may be connected to the anode pad 184 and cathode pad186, respectively, using internal vias and/or conductive layers 196 thatextend in and/or around the body 182. The carrier wafer 180 may alsoinclude electrostatic discharge protection devices therein. In someembodiments, the body 182 comprises silicon and the vias 196 may befabricated using conventional Through Silicon Via (TSV) technology. Insome embodiments, the carrier wafer 180 is about 100 μm thick, and inother embodiments, the carrier wafer may be between about 30 μm andabout 500 μm thick. The anode and cathode pads and the packaged deviceanode and cathode may be less than about 10 μm thick, in someembodiments.

In FIG. 1B, the anode pad 184 and the packaged device anodes 192 are ofapproximately the same size and shape. Moreover, the cathode pads 186and the packaged device cathodes 194 are also of approximately the samesize and shape. However, this need not be the case. For example, asshown in FIG. 1K, the packaged device anodes 192 and/or the packageddevice cathodes 194 may be smaller than the corresponding anode pads 184and cathode pads 186. Thus, more separation may be provided between thepackaged device anodes 192 and cathodes 194 to provide a morepackage-friendly environment, since the placement ability at thepackaging manufacturing level may be lower. As illustrated in FIG. 1K, awider gap between the packaged device anode 192 and the packaged devicecathode 194 may be provided. Thus, the packaged device anodes 192 and/orthe packaged device cathodes 194 may be configured for surface mounting.Accordingly, FIGS. 1B and 1K illustrate a carrier wafer that includesarrays of contacts on opposing faces thereof, and an array of throughvias that electrically connect a respective contact on the opposingfaces to one another. Moreover, FIG. 1K illustrates embodiments whereinthe corresponding contacts in the arrays of contacts on the opposingfaces have different dimensions therebetween.

More specifically, FIGS. 1Q and 1R illustrate configurations of anodepads 184, packaged device anodes 192, cathode pads 186 and packageddevice cathodes 194 on a carrier wafer 180, according to variousembodiments described herein. As shown in FIG. 1Q, the packaged deviceanode 192 may be larger than the anode pad 184, and the packaged devicecathode 194 may be smaller than the cathode pad 186, to facilitatesurface mounting of the LED. In other embodiments, as shown in FIG. 1R,there may be more spacing between the packaged device anode 192 and thepackaged device cathode 194, than between the anode pad 184 and thecathode pad 186, to facilitate surface mounting of the LED. Moreover, afeature, such as a notch 193 in the packaged device cathode 194 may beprovided to allow identification of an orientation of the LED. Othertypes of orientation identification features may also be providedaccording to various other embodiments, and the orientationidentification features may be provided in the packaged device anode192, in the packaged device cathode 194 and/or on the body 180 of thecarrier die. Accordingly, the carrier die may be configured for surfacemounting of the LED and/or to allow identification of an orientation ofthe LED. In some embodiments, when the carrier has dimensions of about0.7 mm×0.7 mm, the packaged device cathode 194 may have dimensions ofabout 0.65 mm×about 0.25 mm, the packaged device anode 192 may havedimensions of 0.65 mm×0.25 mm, and the spacing between the packageddevice anode 192 and the packaged device cathode 194 may be about 0.15mm.

FIG. 1A illustrates LED wafers that are configured for flip-chipmounting on a carrier wafer such as the carrier wafer 180 of FIG. 1B.Various configurations of flip-chip mounted light emitting diode diesmay be used in the LED wafers in various embodiments described herein.Other light emitting devices according to various embodiments describedherein may be configured for non-flip-chip mounting on a mountingsubstrate, as described and illustrated, for example, in U.S. PatentApplication Publication 2011/0031502 to Bergmann et al. entitled “LightEmitting Diodes Including Integrated Backside Reflector and Die Attach”,filed Aug. 10, 2009, assigned to the assignee of the presentapplication, the disclosure of which is hereby incorporated herein byreference in its entirety as if set forth fully herein. Moreover, otherlight emitting devices according to various embodiments described hereinmay be configured as vertical light emitting devices, as described andillustrated, for example, in U.S. Pat. No. 6,791,119 to Slater, Jr etal., entitled “Light Emitting Diodes Including Modifications for LightExtraction”, filed Jan. 25, 2002, assigned to the assignee of thepresent application, the disclosure of which is hereby incorporatedherein by reference in its entirety as if set forth fully herein.

FIG. 1B also illustrates a plurality of scribe lines 190 in the secondface 182 b of the carrier wafer 180, that define a plurality of carrierdies that are of similar length and width as the plurality of LED dies110′ on the LED wafer 100. Scribing may take place using a diamond tool,a laser and/or other conventional scribing techniques. Moreover,scribing may not need to be performed in FIG. 1B, but may be performedafter attaching the LED wafer 100 to the carrier wafer 180, as will bedescribed below.

Accordingly, FIG. 1A illustrates providing an LED wafer 100 thatincludes a plurality of LED dies 110′ on an LED substrate 120, theplurality of LED dies 110′ including anode and cathode contacts 160,170, on a face 110 a thereof that is remote from the LED substrate 120.FIG. 1B illustrates providing a carrier wafer 180 and also illustratesan optional scribing 190 of the carrier wafer, to define a plurality ofcarrier dies 180′ that are of similar length and width as the pluralityof LED dies 110′.

Referring now to FIG. 1C, the LED wafer 100 and the carrier wafer 180are joined, so that the anode and cathode contacts 160, 170 are adjacentthe carrier wafer 180, and the LED substrate 120 is remote from thecarrier wafer 180. More specifically, as illustrated in FIG. 1C, the LEDwafer 100 is mounted on the carrier wafer 180, such that the first face110 a is adjacent the first carrier wafer face 182 a, the second face110 b is remote from the carrier wafer 180, the anode pads 184 areadjacent the anode contacts 160, and the cathode pads 186 are adjacentthe cathode contacts 170. In some embodiments, a bonding layer, such asa eutectic gold/tin solder layer 188, is used to electrically, thermallyand/or mechanically connect the anode contacts 160 to the anode pads184, and the cathode contacts 170 to the cathode pads 186. In otherembodiments, direct attachment of the anode contacts 160 to the anodepads 184, and direct attachment of the cathode contacts 170 to thecathode pads 186 may be provided, for example using thermocompressionbonding and/or other techniques.

Referring now to FIG. 1D, the LED substrate 120 that is joined to thecarrier wafer 180 is shaped. In FIG. 1D, shaping takes place by formingbevels 210 in the second face 120 b of the substrate 120, for exampleusing a saw blade, laser, wet and/or dry etching, and/or otherconventional beveling techniques. Various shapes of beveling and/orfaceting may be provided. For example, an “X”-shaped cut may beperformed on the outer face, and sidewall beveling 210 may also beperformed. Prior to or after beveling, the substrate 120 may be thinned.In other embodiments, the entire LED substrate 120 may be removed.Moreover, in some embodiments, if scribing of the carrier wafer 180 didnot take place prior to attachment in FIG. 1C, scribing may take placeafter attachment in FIG. 1D.

In FIG. 1D, the bevels 210 extend into the second face 120 b of thesubstrate 120. However, deeper beveling may also be provided thatextends through the substrate 120. In other embodiments, the bevels mayextend into, and in some embodiments through, the diode regions 110. Inyet other embodiments, the bevels may extend into the body 182 of thecarrier wafer 180. Thus, for, example, as illustrated in FIG. 1L, thebevels 210′ extend through the substrate 120, through the diode region110 and into the body 182 of the carrier wafer 180. By providing deeperbevels, a subsequent coating of phosphor (described below) can extendalong the edges or sidewalls of the diode region 110, and can reduce orprevent production of undesired edge emission from the LED. For example,undesired blue edge emission may be reduced or prevented when a blue LEDis used with yellow phosphor that extends along the edge or sidewalls ofthe diode region.

As was also noted above, in some embodiments, the entire LED substrate120 may be removed. Thus, as illustrated in FIG. 1M, the substrate 120is entirely removed. Substrate removal may take place prior to or afterbeveling. In other embodiments, the substrate may be thinned prior tobeveling, and the remaining substrate may be removed after beveling.

Referring now to FIG. 1E, a wavelength conversion material 220 isapplied to the LED substrate 120 that has been shaped. The wavelengthconversion material 220, also generally referred to herein as“phosphor”, may be provided according to various configurations. In someembodiments, the diode regions 110 are configured to emit blue light,for example light having a dominant wavelength of about 450-460 nm, andthe wavelength conversion layer 220 comprises yellow phosphor, such asYAG:Ce phosphor, having a peak wavelength of about 550 nm. In otherembodiments, the diode region 110 is configured to emit blue light uponenergization thereof, and the wavelength conversion material 220 maycomprise a mixture of yellow phosphor and red phosphor, such CASN-basedphosphor. In still other embodiments, the diode region is configured toemit blue light upon energization thereof, and the wavelength conversionmaterial 220 may comprise a mixture of yellow phosphor, red phosphor andgreen phosphor, such as LuAG:Ce phosphor particles. Moreover, variouscombinations and subcombinations of these and/or other colors and/ortypes of phosphors may be used in mixtures and/or in separate layers,Various techniques may be used to apply the phosphor, includingspraying, coating and/or other techniques. Phosphor preforms also may beapplied.

Similarly, for deep beveling embodiments that were illustrated in FIG.1M, a wavelength conversion material 220 may be applied according to anyof the embodiments described above, as illustrated, for example, in FIG.1N. As was already noted, by coating the diode region 110 with phosphor,undesired emission of, for example, excess blue light from the sidewallsor edge of the diode region may be reduced or prevented.

Referring now to FIG. 1F, singulation 230 is then performed on thecarrier wafer 180 that has been scribed, and on the LED wafer 100 thathas been joined to the carrier wafer 180 and that has been shaped 210and that has wavelength conversion material 220 applied thereto.Singulation may take place along singulation lines 230, that correspondto the scribe lines 190, using conventional singulation techniques. Asshown in FIG. 1G, the singulation provides a plurality of LED dies 110′,a respective one of which is joined to a respective carrier die 180′. Ananode 192 and a cathode 194 are provided on the carrier die 182, remotefrom the LED die 110. Moreover, a substrate 120 may also be provided.Note that only one of these LED dies/carrier dies is shown in FIG. 1G,FIG. 10 illustrates a singulated LED device of FIG. 1N, wherein thesubstrate 120 is not included, and the phosphor coating 220 extendsalong the sidewalls of the LED dies 110′.

Referring back to FIG. 1D, substrate shaping by beveling wasillustrated. However, other techniques of substrate shaping may beprovided, as will now be described in connection with FIGS. 1H-1J,Specifically, FIG. 1H illustrates providing texturing 212 on the outersubstrate face, followed by application of wavelength conversionmaterial 220. Texturing may take place using etching and/or othertechniques. Substrate thinning may also take place. In otherembodiments, the entire LED substrate 120 may be removed, and texturingof the second face of the diode regions 110 may take place.

FIG. 11 illustrates singulation of the textured devices, as was alsoillustrated in FIG. 1F. FIG. 1J illustrates a resulting LED die 110″having a textured substrate. It will also be understood that, in otherembodiments, beveling and texturing may be combined, for example byusing a saw blade to provide the bevels of FIG. 1D and then texturing onthe exposed surface as illustrated in FIG. 1H, In yet other embodiments,the substrate 120 may be removed, and texturing of the second (outer)face 110 b of the LED 110′ may be provided. FIG. 1P illustrates thesingulation of the textured devices, which were subject to deepbeveling, as was illustrated in FIG. 1N. The texturing may extend on thesecond (outer) face 110 b of the LED die 110″ and/or may extend alongthe sidewalls thereof In addition, an X-cut may also be provided on thesecond face 110 b of the LED die 110″.

FIGS. 1S-1U also illustrate singulation of the devices according tovarious other embodiments described herein. Specifically, in FIG. 1S,the deep beveled wafers of FIG. 1L that include a shaped substrate 120are singulated after a phosphor layer is applied thereto. Thus, as shownin FIG. 1S, the semiconductor LED die 110′ includes an outer face 120 b,an inner face 110 a, and a plurality of sidewalls 110 c therebetween.The carrier die 180′ includes an outer face 182 a, an inner face 182 b,and a plurality of sidewalls 182 c therebetween. The inner face 110 a ofthe LED die 110′ is electrically connected to the inner face 182 b ofthe carrier die 182. A phosphor layer 220 extends directly on the outerface 120 b of the LED die 110′, directly on the plurality of sidewalls110 c of the LED die 110′ and directly on the plurality of sidewalls 182c of the carrier die. In some embodiments, the phosphor layer covers theouter face 120 b of the LED die 110′ and the plurality of sidewalls 110c of the LED die 110′, and partially covers the plurality of sidewalls182 c of the carrier die 180′. As also shown in FIG. 1S, the phosphorlayer 220 may protrude beyond the carrier die 182 in a direction alongthe inner face 182 b and outer face 182 a of the carrier die 180′. Thus,in FIG. 15, the phosphor layer may protrude in the horizontal directionbeyond the sidewalls 182 c of the carrier die body 182. The extent ofprotrusion of the phosphor layer 220 may be controlled, for example, bythe depth and/or profile of the shaping that takes place, by thethickness of the phosphor layer that is provided and/or by othertechniques.

FIG. 1T illustrates other embodiments wherein texturing 212 of the outerface 120 b of the semiconductor LED die 120 is provided, as was alsoillustrated, for example, in FIG. 1J.

FIG. 1U illustrates the addition of a protective layer 222 on thephosphor layer 220. In some embodiments, the phosphor layer 220 maycomprise phosphor particles in a binder, such as a silicone binder, andthe protective layer 222 may comprise a layer, such as a silicone layer,comprising for example the same silicone as the silicone binder, that isfree of the phosphor particles therein. The protective layer 220 may beadded prior to and/or after singulation.

FIGS. 1G, 1J, 1O, 1P, 1S, 1T and 1U also illustrate LEDs according toother embodiments that comprise a carrier 180′, an LED epi region 110, aprimary optic, such as substrate 120, that is distinct from the LED epiregion 110, and a phosphor layer 220. The carrier 180′, the LED epiregion 110, the primary optic 120 and the phosphor layer 220 have outeredges that are within 100 μm of one another in some embodiments, and inother embodiments, have same size outer edges. In some embodiments, theprimary optic can be other suitable materials and/or constructions, suchas a molded silicone lens, for example when the substrate is removed.

FIG. 2 illustrates the packaging of an LED die, for example an LED dieof FIGS. 1G, 1J, 1O, 1P and/or 1S-1U, into an LED fixture. Specifically,as shown in FIG. 2, at least one of the LED dies 320, which maycorrespond to the product of FIGS. 1G, 1J, 1O, 1P and/or 1S-1U isdirectly mounted on a light fixture mounting board 310. The lightfixture mounting board 310 is then mounted in a light fixture housing330 to provide a light fixture 340. As illustrated in FIG. 2, the lightfixture is free of a dome between the LED die 320 and the light fixturehousing 330. It will be understood that, as used herein, a “dome” mayinclude a smooth or faceted structure. It will be understood that lightfixture 340 is illustrated in FIG. 2 in a greatly simplified form, anddoes not include driver circuitry, power supplies, heat sinking and/orother conventional elements. Moreover, the housing 330 may includeopaque/reflective portions 330 a and transparent portions 330 b, toallow light to emerge from the housing.

FIG. 3 is a flowchart of LED fixture manufacturing according to variousembodiments described herein. Referring to FIG. 3, an LED wafer isfabricated at Block 410, for example as was illustrated in FIG. 1A. AtBlock 420, a carrier wafer is fabricated, as was illustrated, forexample, in FIGS. 1B or 1K, and is optionally scribed. At Block 430, theLED wafer and the carrier wafer are joined, as was illustrated, forexample, in FIG. 1C. Scribing also may optionally take place. Thesubstrate is then shaped at Block 440, as was illustrated, for example,in FIGS. 1D, 1H, 1L and/or 1M. At Block 450, phosphor is applied, as wasillustrated, for example, in FIGS. 1E, 1H and/or 1N.

As also illustrated in FIG. 3, all of the operations of Blocks 410-450may take place at a “chip factory”. Thus, substrate carrier joining(Block 430), substrate shaping (Block 440) and phosphor application(Block 450) may be performed at a wafer level at a chip factory ratherthan being applied at a die level at a package factory.

Continuing with the description of FIG. 3, testing of the wafers thatare provided by the chip factory at Block 450 may then be performed atBlock 460 and singulation may also be performed at Block 460, as wasillustrated, for example, in FIGS. 1F and/or 1H. Testing may beperformed prior to and/or after singulation at Block 460. Testing andsingulation may take place at a separate “module factory”, or may takeplace at the chip factory or at a “fixture factory”. Accordingly, insome embodiments, the completed wafers from Block 450 may be shipped toa fixture factory, which is then responsible for testing, singulationand integration into a fixture. Optionally, the entire carrier die 180′of FIGS. 1G or 1J may be removed at any desired point in the fixturemanufacturing process, if desired. Then, at Block 480, the LED, forexample the LED of FIGS. 1G, 1J, 1O, 1P and/or 1S-1U, is mounted on afixture board, as was illustrated, for example, in FIG. 2, and at Block490, the fixture board is mounted on the fixture housing, as also wasillustrated in FIG. 2.

Various embodiments described herein, as illustrated, for example, inFIG. 3, may eliminate the need for a package factory and may alsoeliminate the need for a module factory. The chip maker may shipcompleted wafers from the chip factory to a fixture factory or a modulefactory.

In sharp contrast, FIG. 4 provides an overview of conventional fixturemanufacturing. An LED wafer is fabricated and singulated at chipfactory, as illustrated in Block 510. The singulated LED chips are thenplaced on die sheets and sent to a package factory, where the dies arepackaged at Block 520. For example, the dies are mounted on a submountor other substrate, encapsulated, and a dome is placed on theencapsulated package. The packaged LEDs are then shipped to a modulefactory or a fixture factory, where they are mounted on a fixture board,as shown at Block 530. At the fixture factory, the packaged LEDs aremounted in a fixture housing, as shown at Block 540.

FIG. 5 illustrates a more detailed flowchart of conventional fixturemanufacturing. As illustrated at Block 610, the LED wafer is fabricated.Then, at Block 620, wafer level operations are performed (e.g., diecontact formation and electrical testing). At Block 630, the LED diesare singulated, tested and sorted. At Block 640, the sorted LED dies areassembled onto sorted die sheets. The sorted die sheets are then shippedto a package factory, where at Block 660, a panel is populated andphosphor is applied, and the panel is tested, singulated, packaged andsorted again. Finally, operations of Block 530 and 540 are performed.

As was described above, various embodiments described herein can provideimproved efficiency in the fabrication process for LEDs byeliminating/reducing fabrication steps and even eliminating the need forone or two separate factories (a packaging factory and/or a modulefactory). Moreover, improved luminous efficiency also may be providedaccording to various embodiments described herein. For example, FIG. 6illustrates an LED light fixture 340 that includes a light fixturemounting board 310 and a plurality of LED dies 110′/110″, such as theLED dies of FIG. 1G, 1J, 1O, 1P and/or 1S-1U directly mounted thereon.LED dies according to any of the embodiments described herein may beused. A light fixture housing 330 is provided, wherein the light fixturemounting board 310 including the plurality of LED dies 110′/110″ mountedthereon, is mounted in the housing 330. As shown in FIG. 6, the LED diesmay be mounted in the housing without the need for encapsulation and adome. Thus, the light fixture 340 is free of a dome between a respectiveLED die 110′/110″ and the light fixture housing 330. Because a dome isnot needed, the LEDs may be packed much more tightly than isconventionally the case. Higher light output per unit area may therebybe provided. Moreover, although embodiments of FIG. 1G are illustratedin FIG. 6, the carrier dies 180′ may optionally also be removed from theLED dies 110′ prior to mounting on the LED mounting board 310, so thatthe plurality of LED dies 110′ may be directly mounted on the lightfixture mounting board without a carrier die therebetween.

FIG. 7 is a flowchart of LED wafer/carrier wafer fabrication accordingto various other embodiments. As illustrated in FIG. 7, an LED wafer 100is manufactured at Block 702, as was illustrated, for example, in FIG.1A, and wafer processing is performed at Block 704 in order to providestandard wafer fabrication operations including metallization. At Block706, substrate shaping, such as substrate thinning including substrateremoval and/or texturing may optionally take place, to provide a finalLED wafer thickness of, for example, between about 330 μm and about 390μm, as was illustrated, for example, in FIG. 1M. At Block 712, acarrier, such as a silicon wafer, is fabricated, through vias are formedat Block 714 and both faces of the carrier wafer are patterned at Block716 to provide contacts, as was illustrated, for example, in FIGS. 1Band 1K. At Block 722, the wafer and carrier are aligned and then bondedat Block 724, for example using eutectic bonding, as was illustrated,for example, in FIG. 1C. The bonded devices then proceed to backendprocessing operations at Block 726, as will be described in FIG. 8. Itwill be understood by those having skill in the art that all of theoperations of FIG. 7 may be performed at a chip factory, also commonlyreferred to as a “Fab”.

FIG. 8 illustrates the backend processing flow that may also take placeat a chip factory or at a module/fixture factory. Referring to FIG. 8,at Block 732, the LED wafer and carrier that are bonded together ismounted on a tape. At Block 734, wafer shaping may take place ifapplicable. The shaping may include forming an “X”-cut or other top cutalong with other operations to texture the LED substrate or the LED die,as was illustrated, for example, in FIG. 1H. A bevel cut may also beperformed at Block 734, as was illustrated, for example, in FIGS. 1D, 1Land/or 1M. Scribing of the carrier may also take place at Block 736using, for example, a straight cut, as was illustrated, for example, atFIG. 1C. A post-saw cleanup using, for example, Reactive Ion Etching(RIE) can then be performed. Phosphor and an optional protective layerare then deposited, for example by spraying or other coating techniquesat Block 738, as was illustrated, for example, in FIGS. 1E, 1H and 1N.An initial probe, such as a color target probe, may be performed.Singulation then takes place at Block 742, for example by taking apartthe dies using a slotted anvil, as was illustrated, for example, inFIGS. 1F and 1I. The tape may then be stretched to further separate thesingulated devices and a post-stretch cure of the tape may then beperformed if desired. Electrical and optical testing may then take placeat Block 744 and an optical inspection, such as a visual inspection, maytake place at Block 746. The LEDs are then binned and sorted at Block748. It will be understood that operations 732-748 of FIG. 8 may alltake place at the chip factory.

FIGS. 9A, 9B, 10A and 10B illustrate an increased packing density orlight output per unit area/volume/height that may be provided accordingto various embodiments described herein. FIG. 9A is a cross-section andFIG. 9B is a plan view of a mounting board 310 with a plurality of LEDs900 mounted thereon, according to any of the various embodimentsdescribed herein. For ease of illustration, the connectors and contacts,the internal structure of the LED and the phosphor/protective layers arenot illustrated. As shown, the carrier substrate 180′ may be ofapproximately same size as the LED epi region 110. In other embodiments,the LED die and the carrier die have sides that are within 100 μm orwithin about 15% of one another in length. In other embodiments, the LEDdie and the carrier die have areas that are within 70% of one another,in other embodiments within 85% of one another, and in still otherembodiments have same areas. Moreover, a dome or other separate lensneed not be provided. Accordingly, packing on the fixture mounting board310 may be dense.

In sharp contrast, FIG. 10A illustrates conventional packing of LED 810on a carrier substrate 820, also referred to as a submount, which is inturn mounted on a fixture mounting board 310. Each LED 800 also includesan associated dome 830 thereon. The submount 820 typically needs to bemuch bigger than the LED die 810 in order to accommodate the domethereon. Accordingly, the packing density is generally much lower thanmay be provided according to various embodiments described herein.

For example, consider that the LED epi region 110 of FIGS. 9A and 9B andthe LED die 810 of FIGS. 10A and 10B are both about 1.0×1.0 mm in size.The carrier substrate 180′ of FIGS. 9A and 9B may be slightly larger,for example about 1.1×1.1 mm in size. Thus, according to variousembodiments described herein, the carrier substrate 180′ of FIGS. 9A and9B may be about the same size as the LED epi region 110. The spacingbetween adjacent LEDs 900, shown as “x” in FIGS. 9A and 9B, may be about100 μm in this example. Other LED epi region 110 and die sizes that maybe used include 0.5 mm×0.5 mm.

In sharp contrast, in FIGS. 10A and 10B, the submount 820 is much largerthan the LED die 810, for example at least about 3×3 mm in size usingthe same LED die size (about 1.0×1.0 mm) as FIGS. 9A/9B. This largersize submount 820 is needed to hold the dome 830. Therefore, thedistance “y” between adjacent LED dies 810 may be about 2000 μm,assuming the same submount spacing x. Thus, embodiments of FIGS. 10A-10Bhave much lower die packing density on the mounting board 310 thanvarious embodiments described herein, for example in FIGS. 9A and 9B.Embodiments of FIGS. 9A and 9B can therefore provide for greater lightoutput per unit area of the mounting board 310.

A comparison between existing LEDs, as illustrated by LEDs 800 of FIGS.10A and 10B, and LEDs according to various embodiments described herein,as illustrated by LEDs 900 of FIGS. 9A and 9B, will now be provided, toquantitatively illustrate the higher optical efficiency that may beprovided according to various embodiments described herein.

Specifically, LEDs 800 of FIGS. 10A and 10B may be represented by aCree® XLamp® XB-D white LED, as described extensively in the ProductFamily Data Sheet entitled “Cree® XLamp® XB-D White LED”, Cree DocumentNo. CLD-DS45 Rev 4, 2011-2012, the disclosure of which is herebyincorporated herein by reference in its entirety as if set forth herein.As described in this Data Sheet, an XB-D LED die 810 may have dimensionsof 0.7 mm×0.7 mm, or about 0.5 mm². The submount or carrier 820 may havedimensions of 2.45 mm×2.45 mm, or about 6 mm². The total height of theXB-D LED may be 1.84 mm, with the total thickness of the carrier being0.76 mm and the total thickness of the dome 830 being 108 mm. As notedon the first page of the above-cited Product Family Data Sheet, the XB-Dwhite LED constitutes Cree's smallest lighting class LED, and mayproduce up to 136 lumens/watt (lm/w) of cool white light at a standardtemperature of 85° C. and a standard drive current of 350 mA.Accordingly, on a per-unit area basis, the XB-D LED may produce up to136 lm/w/(2.45 mm×2.45 mm) or about 22 lumens per watt per squaremillimeter.

In sharp contrast, various embodiments described herein, as illustratedin FIG. 9A, may use the same 0.7 mm×0.7 mm LED die 110 as the XB-D LEDand may use a carrier die 180′ that is also about 0.7 mm×0.7 mm in size.As shown in FIG. 11, various samples of these devices produced betweenabout 105 and about 110 lumens of cool white light (between about 6100and 6500 K in FIG. 11) for an average output of about 107 lumens perwatt. Thus, an LED according to various embodiments described herein mayproduce 107 lm/w/(0.7 mm×0.7 mm), or at least about 200 lumens per wattper square millimeter. This constitutes an almost tenfold improvement inlumens per watt per square millimeter over the XB-D LED.

Accordingly, various embodiments described herein may provide asemiconductor LED die 900 that includes an LED epi region 110 and acarrier die 180′ that is electrically connected to the semiconductor LEDdie 110, wherein the LED epi region 110 and the carrier die 180′ havesides that are within 100 μm of one another, or within 15% of oneanother, in length. In some embodiments, the LED epi region 110 and thecarrier die 180′ have same side lengths. In other embodiments, the sizedifference between the LED epi region 110 and the carrier die 180′ ofFIG. 9A may be less than about 100 μm, less than about 200 μm, less thanabout 500 μm, less than about 10%, less than about 5% and, in variousembodiments, may be substantially zero (so that the LED epi region 110and the carrier substrate 180′ may be about the same size). Theserelationships may apply to any carrier die and LED die that are smaller,larger or different from various embodiments described herein. In someembodiments, these LEDs can produce at least 45 lumens per watt persquare millimeter of, in some embodiments, cool white light (about 6000K). In other embodiments, these LEDs can produce at least 100 lumens perwatt per square millimeter, and in yet other embodiments, these LEDs canproduce at least about 200 lumens per watt per square millimeter of, insome embodiments, cool white light (about 6000 K). For warm white light,these values may be decreased by about 30%, so that various embodimentsdescribed herein can produce at least 30 lumens of warm white light(about 3000 K) per watt per square millimeter, and in some embodiments,70 lumens of warm white light per watt per square millimeter, and in yetother embodiments, at least about 140 lumens of warm white light perwatt per square millimeter of area of the carrier die.

The comparative output of the XB-D LED of FIGS. 10A-10B and LEDsaccording to various embodiments described herein, may also be providedon a “per volume” (mm³) basis. As used herein, “volume” means theproduct of the area of the carrier die and the total height of the LED,and does not take into account the decreased volume caused by the shapeof the dome 830 and/or beveling of the LED die. As described in theabove-cited Product Family Data Sheet, the XB-D LED may have a totalheight of about 1.84 mm, so that its total output per unit volume may becalculated as 136 lm/w/(2.45 mm×2.45 mm×1.84 mm), or about 12 lumens perwatt per cubic millimeter. In sharp contrast, various embodiments asillustrated in FIGS. 9A and 9B, may have a total height of about 1 mm,so as to produce at least 45 lumens per watt per cubic millimeter ofvolume of the LED in some embodiments, at least about 100 lumens perwatt per cubic millimeter of volume of the LED in other embodiments, andat least about 200 lumens per watt per cubic millimeter of volume of theLED in yet other embodiments, of cool white light. Warm white lightvalues may be decreased by about 30%, to produce at least 30 lumens ofwarm white light per cubic millimeter of volume of the LED in someembodiments, at least 70 lumens of warm white light per watt per cubicmillimeter of volume of the LED in other embodiments, and at least about140 lumens of warm white light per watt per cubic millimeter of volumeof the LED in yet other embodiments.

As was described above, various embodiments described herein can providevery small LED die/carrier packages compared to, for example, XB-D LEDsdescribed in the above-cited Product Family Data Sheet. As was describedabove, the XB-D LED has an area of about 2.45 mm×2.45 mm or about 6 mm².In contrast, using the same LED die size of 0.7 mm×0.7 mm, variousembodiments described herein may have area of about 0.5 mm². Otherembodiments described herein may use a larger die size and a largercarrier size to produce an area of less than about 1 mm², and yet otherembodiments may further increase the die and carrier size to produce anarea of less than about 2 mm². Smaller die sizes may also be used.Moreover, the height of various embodiments described herein may be lessthan about 1.5 mm in other embodiments.

Other dimensions of various embodiments described herein will now beprovided. Specifically, the carrier die 180 may have a thickness ofbetween 50 μm and about 100 μm, and the LED die (epi region 110 andsubstrate 120) may have a thickness of between about 100 μm and about1000 μm, and in some embodiments may be about 150 μm, about 250 μm orabout 400 μm thick, and in some embodiments less than about 500 μmthick. A specific embodiment may use a carrier die that is about 100 μmthick and an LED die that is about 335 μm thick. Specific thicknessesfor an LED die that is 240 mm×320 mm in area may be about 140 μm; for anarea of 500 mm×500 mm may be about 250 μm; for an area of 350 mm×470 mmmay be about 155 μm; for an area of about 700 mm×700 mm, 850 mm×850 mm,1000 mm by 1000 mm or 1400 mm×1400 mm may be about 355 μm. Moreover,commercially available sapphire die may be between 85 μm and about 150μm thick, and typically less than about 200 μm thick. A phosphor coatingmay be added in some embodiments, which may have a thickness of lessthan about 1 mm in some embodiments, between 10 μm and 500 μm in otherembodiments, and in yet other embodiments between about 20 μm and about60 μm.

Accordingly, an LED according to various embodiments described hereinmay comprise a semiconductor LED die that includes an LED epi region anda carrier die that is electrically connected to the LED die, wherein theLED epi region and the carrier die have sides that are within 100 μm ofone another in length and, in some embodiments, have the same sidelengths. Moreover, these LEDs may be combined with a light fixturemounting board on which the LED die is mounted and a light fixturehousing in which the light fixture mounting board is mounted to providea light fixture, wherein the light fixture is free of a dome between theLED die and the light fixture housing.

Other embodiments may provide an LED light fixture that includes a lightfixture mounting board, a plurality of LEDs mounted on the light fixturemounting board, and a light fixture housing in which the light fixturemounting board including the plurality of LEDs thereon is mounted. Thelight fixture is free of a dome between a respective LED and the lightfixture housing.

FIGS. 12-16 provide photographs of prototype LEDs according to variousembodiments described herein. These figures are provided to highlightthe scale and/dimensional relationships between the various features ofthe prototype LEDs, such as the carrier, the epi region, the primaryoptic and the phosphor layer, according to various embodiments describedherein. Specifically, FIG. 12A, is a side photograph, FIG. 12B is abottom photograph, FIG. 12C is another side photograph and FIGS. 12D and12E are top photographs of a prototype LED according to variousembodiments described herein. FIG. 13A provides a more detailed bottomphotograph, and FIG. 13B provides a more detailed top photograph. FIG.13C provides a side photograph with dimensions, based on a carrier dieand substrate die that are 0.7 mm×0.7 mm in size.

FIG. 14 provides photographs of a wafer after singulation, a prototypeLED component, a backside contact and a prototype LED under bias. FIG.15 illustrates relative sizes of various LEDs, such as XM-L highvoltage, XT-E and XB-D LEDs available from the assignee, Cree, Inc.wherein a 0.7 mm×0.7 mm LED according to various embodiments describedherein is illustrated at the far right and is labeled “WLP”. Finally,FIG. 16 provides photographs of an LED according to various embodimentsdescribed herein after die separation, and when mounted on a mountingboard and installed in a fixture.

Accordingly, various embodiments described herein can move testing andsingulation to the very end of the wafer level processing. Productionefficiency and/or luminous efficiency may thereby be improved.

Various embodiments have been described herein in connection withoperational flowcharts including flowchart blocks. It should be notedthat in some alternate embodiments, the functions/acts noted in theblocks may occur out of the order noted in the flowcharts unlessexpressly stated to the contrary herein. For example, two blocks shownin succession may in fact be executed substantially concurrently or theblocks may sometimes be executed in the reverse order, depending uponthe functionality/acts involved, unless expressly stated to the contraryherein. Moreover, the functionality of a given block of the flowchartsmay be separated into multiple blocks and/or the functionality of two ormore blocks may be at least partially integrated. Finally, other blocksmay be added/inserted between the blocks that are illustrated.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, the present specification, including the drawings, shall beconstrued to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

What is claimed is:
 1. A method of fabricating a plurality of LightEmitting Diodes (LEDs), the method comprising: providing an LED waferthat includes a plurality of LED dies on an LED substrate, the pluralityof LED dies including anode and cathode contacts on a face thereof thatis remote from the LED substrate; providing a carrier wafer; joining theLED wafer and the carrier wafer so that the anode and cathode contactsare adjacent the carrier wafer and the LED substrate is remote from thecarrier wafer; shaping the LED wafer that is joined to the carrierwafer; applying wavelength conversion material to the LED wafer that isshaped; and singulating the carrier wafer and the LED wafer that hasbeen joined to the carrier wafer and that has been shaped and that haswavelength conversion material applied thereto to provide a plurality ofLED dies, a respective one of which is joined to a respective carrierdie, and having a length and width similar to the carrier die to whichit is joined.
 2. A method according to claim 1 further comprising:scribing the carrier wafer to define the plurality of carrier dies thathave length and width similar to the plurality of LED dies;
 3. A methodaccording to claim 2 wherein the scribing is performed before or afterthe joining.
 4. A method according to claim 1 wherein the shapingcomprises beveling the LED substrate.
 5. A method according to claim 1wherein the shaping comprises texturing the LED substrate.
 6. A methodaccording to claim 1 wherein the shaping comprises thinning or removingthe LED substrate.
 7. A method according to claim 6 wherein the thinningor removing is followed by texturing the LED dies.
 8. A method accordingto claim 5 wherein the shaping further comprises beveling the LEDsubstrate.
 9. A method according to claim 6 wherein the shaping furthercomprises beveling the LED dies.
 10. A method according to claim 1wherein the LED dies and the carrier dies have sides that are within 100μm of one another in length.
 11. A method according to claim 1 whereinthe LED dies and the carrier dies have same side lengths.
 12. A methodaccording to claim 1 wherein singulating is followed by: removing therespective carrier die.
 13. A method according to claim 1 whereinsingulating is followed by: mounting at least one of the LED diesdirectly on a light fixture mounting board; and mounting the lightfixture mounting board including the at least one of the LED diesmounted directly thereon in a light fixture housing to provide a lightfixture.
 14. A method according to claim 13 wherein the mounting atleast one of the LED dies directly on a light fixture mounting board andthe mounting the light fixture mounting board including the at least oneof the LED dies mounted directly thereon in a light fixture housing toprovide a light fixture are performed without providing a dome on the atleast one of the LED dies.
 15. A method according to claim 1 whereinproviding a carrier wafer comprises providing a carrier wafer includingarrays of contacts on opposing faces thereof and an array ofthrough-vias that electrically connect respective contacts on theopposing faces to one another.
 16. A method according to claim 15wherein corresponding contacts in the arrays of contacts on the opposingfaces have different dimensions therebetween.
 17. A Light Emitting Diode(LED), comprising: a semiconductor LED die that includes an LED epiregion; and a carrier die that is electrically connected to the LED die,wherein the LED epi region and the carrier die have sides that arewithin 100 μm of one another in length.
 18. An LED according to claim 17wherein the LED epi region and the carrier die have same side lengths.19. An LED according to claim 17 wherein the LED produces at least about200 lumens per watt per square millimeter.
 20. An LED according to claim17 wherein the LED produces at least 100 lumens per watt per squaremillimeter.
 21. An LED according to claim 17 wherein the LED produces atleast 45 lumens per watt per square millimeter.
 22. An LED according toclaim 17 wherein the LED produces at least about 140 lumens of warmwhite light per watt per square millimeter.
 23. An LED according toclaim 17 wherein the LED produces at least 70 lumens of warm white lightper watt per square millimeter.
 24. An LED according to claim 17 whereinthe LED produces at least 30 lumens of warm white light per watt persquare millimeter.
 25. An LED according to claim 17 in combination with:a light fixture mounting board on which the carrier die is directlymounted; and a light fixture housing in which the light fixture mountingboard is mounted to provide a light fixture, wherein the light fixtureis free of a dome between the carrier die and the light fixture housing.26. An LED according to claim 17 further comprising an anode and acathode on the carrier die, remote from the LED die.
 27. An LEDaccording to claim 17 wherein the LED die further includes a substrate.28. A Light Emitting Diode (LED), comprising: a semiconductor LED diethat includes an LED epi region; and a carrier die that is electricallyconnected to the LED die, wherein the LED epi region and the carrier diehave sides that are within about 15% of one another in length.
 29. AnLED according to claim 28 wherein the LED epi region and the carrier diehave same side lengths.
 30. An LED according to claim 28 wherein the LEDproduces at least about 200 lumens per watt per square millimeter. 31.An LED according to claim 28 wherein the LED produces at least 100lumens per watt per square millimeter.
 32. An LED according to claim 28wherein the LED produces at least 45 lumens per watt per squaremillimeter.
 33. An LED according to claim 28 wherein the LED producesabout 140 lumens of warm white light per watt per square millimeter. 34.An LED according to claim 28 wherein the LED produces at least 70 lumensof warm white light per watt per square millimeter.
 35. An LED accordingto claim 28 wherein the LED produces at least 30 lumens of warm whitelight per watt per square millimeter.
 36. An LED according to claim 28in combination with: a light fixture mounting board on which the carrierdie is directly mounted; and a light fixture housing in which the lightfixture mounting board is mounted to provide a light fixture, whereinthe light fixture is free of a dome between the carrier die and thelight fixture housing.
 37. An LED according to claim 28 furthercomprising an anode and a cathode on the carrier die, remote from theLED die.
 38. An LED according to claim 28 wherein the LED die furtherincludes a substrate.
 39. A Light Emitting Diode (LED), comprising: asemiconductor LED die; and a carrier die that is electrically connectedto the LED die, wherein the LED produces at least 45 lumens per watt persquare millimeter of area of the carrier die.
 40. An LED according toclaim 39 wherein the LED produces at least 100 lumens per watt persquare millimeter of the area of the carrier die.
 41. An LED accordingto claim 39 wherein the LED produces at least about 200 lumens per wattper square millimeter of the area of the carrier die.
 42. An LEDaccording to claim 39 in combination with: a light fixture mountingboard on which the carrier die is directly mounted; and a light fixturehousing in which the light fixture mounting board is mounted to providea light fixture, wherein the light fixture is free of a dome between thecarrier die and the light fixture housing.
 43. An LED according to claim39 further comprising an anode and a cathode on the carrier die, remotefrom the LED die.
 44. An LED according to claim 39 wherein the LED diefurther includes a substrate.
 45. A Light Emitting Diode (LED),comprising: a semiconductor LED die; and a carrier die that iselectrically connected to the LED die, wherein the LED produces at least30 lumens of warm white light per square millimeter of area of thecarrier die.
 46. An LED according to claim 45 wherein the LED producesat least 70 lumens of warm white light per watt per square millimeter ofthe area of the carrier die.
 47. An LED according to claim 45 whereinthe LED produces at least about 140 lumens of warm white light per wattper square millimeter of the area of the carrier die.
 48. An LEDaccording to claim 45 in combination with: a light fixture mountingboard on which the carrier die is directly mounted; and a light fixturehousing in which the light fixture mounting board is mounted to providea light fixture, wherein the light fixture is free of a dome between thecarrier die and the light fixture housing.
 49. An LED according to claim45 further comprising an anode and a cathode on the carrier die, remotefrom the LED die.
 50. An LED according to claim 45 wherein the LED diefurther includes a substrate.
 51. A Light Emitting Diode (LED),comprising: a semiconductor LED die; and a carrier die that iselectrically connected to the LED die, wherein the LED produces at least45 lumens per watt per cubic millimeter of volume of the LED.
 52. An LEDaccording to claim 51 wherein the LED produces at least 100 lumens perwatt per cubic millimeter of the volume of the LED.
 53. An LED accordingto claim 51 wherein the LED produces at least about 200 lumens per wattper cubic millimeter of the volume of the LED.
 54. An LED according toclaim 51 in combination with: a light fixture mounting board on whichthe carrier die is directly mounted; and a light fixture housing inwhich the light fixture mounting board is mounted to provide a lightfixture, wherein the light fixture is free of a dome between the carrierdie and the light fixture housing.
 55. A Light Emitting Diode (LED),comprising: a semiconductor LED die; and a carrier die that iselectrically connected to the LED die, wherein the LED produces at least30 lumens of warm white light per cubic millimeter of volume of the LED.56. An LED according to claim 55 wherein the LED produces at least 70lumens of warm white light per watt per cubic millimeter of the volumeof the LED.
 57. An LED according to claim 55 wherein the LED produces atleast about 140 lumens of warm white light per watt per cubic millimeterof the volume of the LED.
 58. An LED according to claim 55 incombination with: a light fixture mounting board on which the carrierdie is directly mounted; and a light fixture housing in which the lightfixture mounting board is mounted to provide a light fixture, whereinthe light fixture is free of a dome between the carrier die and thelight fixture housing.
 59. A Light Emitting Diode (LED), comprising: asemiconductor LED die; and a carrier die that is electrically connectedto the LED die, wherein the carrier die has an area of less than about 2square millimeters.
 60. An LED according to claim 59 wherein the carrierdie has an area of less than about 1 square millimeter.
 61. An LEDaccording to claim 60 wherein the LED has an area of about 0.5 squaremillimeter or less.
 62. An LED according to claim 61 wherein the LED hasa height of about 1 millimeter.
 63. An LED according to claim 59 incombination with: a light fixture mounting board on which the carrierdie is directly mounted; and a light fixture housing in which the lightfixture mounting board is mounted to provide a light fixture, whereinthe light fixture is free of a dome between the carrier die and thelight fixture housing.
 64. An LED according to claim 59 furthercomprising an anode and a cathode on the carrier die, remote from theLED die.
 65. An LED according to claim 59 wherein the LED die furtherincludes a substrate.
 66. A Light Emitting Diode (LED), comprising: asemiconductor LED die; and a carrier die that is electrically connectedto the LED die, wherein the LED has a height of less than about 1.5millimeters.
 67. An LED according to claim 66 wherein the LED has aheight of about 1 millimeter.
 68. An LED according to claim 66 incombination with: a light fixture mounting board on which the carrierdie is directly mounted; and a light fixture housing in which the lightfixture mounting board is mounted to provide a light fixture, whereinthe light fixture is free of a dome between the carrier die and thelight fixture housing.
 69. A Light Emitting Diode (LED), comprising: asemiconductor LED die that includes inner and outer faces and aplurality of sidewalls therebetween; a carrier die that includes innerand outer faces and a plurality of sidewalls therebetween, wherein theinner face of the LED die is electrically connected to the inner face ofthe carrier die; and a phosphor layer that extends directly on the outerface of the LED die, directly on the plurality of sidewalls of the LEDdie and directly on the plurality of sidewalls of the carrier die. 70.An LED according to claim 69 wherein the phosphor layer covers the outerface of the LED die and the plurality of sidewalls of the LED die andpartially covers the plurality of sidewalls of the carrier die.
 71. AnLED according to claim 69 wherein the phosphor layer protrudes beyondthe carrier die in a direction along the faces of the carrier die. 72.An LED according to claim 69 further comprising a protective layer onthe phosphor layer, remote from the LED die and the carrier die.
 73. AnLED according to claim 72 wherein the phosphor layer comprises phosphorparticles in a silicone binder and wherein the protective layercomprises a silicone layer that is free of the phosphor particlestherein.
 74. An LED according to claim 69 wherein the carrier die isconfigured for surface mounting of the LED.
 75. An LED according toclaim 69 wherein the carrier die includes a feature configured to allowidentification of an orientation of the LED.
 76. An LED according toclaim 69 further comprising an anode and a cathode on the carrier die,remote from the LED die.
 77. An LED according to claim 69 wherein theLED die further includes a substrate.
 78. A Light Emitting Diode (LED),comprising: a carrier; an LED epi region; a primary optic distinct fromthe LED epi region; and a phosphor layer, wherein the carrier, LED epiregion, primary optic and phosphor layer have outer edges that arewithin 100 μm of one another.
 79. An LED according to claim 78 whereinthe carrier, LED epi region, primary optic and phosphor layer have samesize outer edges.
 80. An LED according to claim 78 in combination with:a light fixture mounting board on which the carrier is directly mounted;and a light fixture housing in which the light fixture mounting board ismounted to provide a light fixture, wherein the light fixture is free ofa dome between the carrier and the light fixture housing.
 81. An LEDaccording to claim 78 further comprising an anode and a cathode on thecarrier, remote from the LED epi region.
 82. An LED according to claim78 further comprising a substrate between the LED epi region and thephosphor layer.
 83. A Light Emitting Diode (LED), comprising: asemiconductor LED die that includes an LED epi region; and a carrier diethat is electrically connected to the LED die, wherein the LED epiregion and the carrier die have areas that are within 70% of oneanother.
 84. An LED according to claim 83 wherein the areas are within85% of one another.
 85. An LED according to claim 83 wherein the LED epiregion and the carrier die have same areas.
 86. An LED according toclaim 83 wherein the LED produces at least about 200 lumens per watt persquare millimeter.
 87. An LED according to claim 83 wherein the LEDproduces at least 100 lumens per watt per square millimeter.
 88. An LEDaccording to claim 83 wherein the LED produces at least 45 lumens perwatt per square millimeter.
 89. An LED according to claim 83 wherein theLED produces at least about 140 lumens of warm white light per watt persquare millimeter.
 90. An LED according to claim 83 wherein the LEDproduces at least 70 lumens of warm white light per watt per squaremillimeter.
 91. An LED according to claim 83 wherein the LED produces atleast 30 lumens of warm white light per watt per square millimeter. 92.An LED according to claim 83 in combination with: a light fixturemounting board on which the carrier die is directly mounted; and a lightfixture housing in which the light fixture mounting board is mounted toprovide a light fixture, wherein the light fixture is free of a domebetween the carrier die and the light fixture housing.
 93. An LEDaccording to claim 83 further comprising an anode and a cathode on thecarrier die, remote from the LED die.
 94. An LED according to claim 83wherein the LED die further includes a substrate.
 95. A Light EmittingDiode (LED) light fixture comprising: a light fixture mounting board; aplurality of LEDs directly mounted on the light fixture mounting board;and a light fixture housing in which the light fixture mounting boardincluding the plurality of LEDs directly mounted thereon is mounted,wherein the light fixture is free of a dome between a respective LED andthe light fixture housing.
 96. A LED light fixture according to claim 95wherein the plurality of LEDs comprise a plurality of semiconductor LEDdies that are directly mounted on the light fixture mounting boardwithout a carrier die therebetween.
 97. A method of manufacturing LightEmitting Diode (LED) light fixtures, the method comprising: fabricatinga plurality of LED wafers including wavelength converting materialthereon at chip factory; dicing the LED wafers including the wavelengthconverting material thereon to produce a plurality of LED dies, andmounting the LED dies on a light fixture mounting board at a modulefactory or at a fixture factory; and mounting the light fixture mountingboard in a light fixture at a fixture factory; wherein the fabricating,the dicing and the mounting bypass LED packaging factories.
 98. A methodaccording to claim 97 wherein the chip, module and fixture factories donot perform an operation of providing domes on the plurality of LEDdies.